1. Field of the Invention
The present invention relates to a touch sensing apparatus, and more particularly, to a touch sensing apparatus and a method of driving the same, for reducing the width of a bezel area while reducing noise of an outermost readout channel.
2. Discussion of the Related Art
Today, a touch sensor that can input information via touch on screens of various display apparatuses has been widely used as an information input apparatus of a computer system. The touch sensor moves or selects displayed information by simply touching a screen via a user finger or a stylus and thus can be easily used regardless of age or sex.
A touch sensing apparatus detects a touch and a touch location on a touch sensor of a display apparatus and outputs touch information, and a computer system analyzes the touch information and executes a command. The display apparatus may mainly use a flat display apparatus such as a liquid crystal display apparatus, a plasma display panel, an organic light emitting diode display apparatus, etc. The touch sensor technologies include a resistance layer method, a capacitive method, an optical method, an infrared type method, an ultrasonic method, an electromagnetic method, etc. according to sensing principles.
A touch sensor may be configured as an on-cell touch sensor that is manufactured in a panel form and is attached onto a display apparatus or may be configured as an in-cell sensor installed in a pixel matrix of a display apparatus. The touch sensor mainly uses a photo touch sensor that recognizes a touch according to variation in light intensity using a photo transistor and a capacitive touch sensor that recognizes a touch according to capacitive variation.
In general, a capacitive touch sensing apparatus includes a touch sensor and a touch controller for driving the touch sensor and sensing capacitance that varies according to touch from the touch sensor to calculate touch coordinates.
A conventional touch sensing apparatus further includes a ground routing line formed on a bezel area corresponding to an edge portion of the touch sensor and connected to a ground in order to prevent electro-magnetic interference (EMI) due to static electricity introduced outside the touch sensing apparatus.
However, as a ground line formed on a bezel area of a touch sensor is located close to an outermost readout channel adjacent to the ground line, parasitic capacitance formed between a ground routing line and an outermost readout channel is increased, thereby increasing parasitic capacitance deviation between outer readout channels positioned on an outer portion. Problems arise in that the noise component of the outermost readout channel is increased in proportion to this parasitic capacitance deviation, thereby reducing the sensing capability of the outermost readout channel.
In order to address these problems, an interval between a ground routing line and an outermost readout channel is increased. In this case, problems arise in that parasitic capacitance variation and noise component due thereto is reduced, whereas the width of an outer bezel area is increased.